The automotive industry has used fibre reinforced composites (FRC) for parts of automobiles, especially high performance cars, and trucks for many years. The use of high speed manufacturing technologies allows carbon fibre reinforced composites (CFRP) to move into serial production vehicles. One such technique is rapid cure press moulding. The substrates used in this process could be from prepreg or from filament wound structures. In the latter, tows of carbon fibre, either pre-impregnated with resin or, more commonly, impregnated in-line, are wound around a rotating mandrel. As the winding head is moved back and forth along the mandrel, it allows a variety of woven structures with numerous interlocking angles to be constructed. The removal of the woven structure from the mandrel creates rectangular “blanks” that can be used as the substrates for rapid press curing in a similar way to prepreg materials.
The industry desires to have such high performance filament winding (FW) resins that can be rapidly processed in order to contain costs and achieve the high throughputs required for serial production. Some of the known resins have low viscosity so as to facilitate impregnation of the fiber. However, we have identified several problems with current filament winding resins. One is that the resins have such low reactivity and viscosity that the materials remain fluid and sticky during handling. This fluidity allows the filament positions to shift and skew altering the woven alignment and angles during and after winding. This could ultimately affect the mechanical performance if the part is stressed in a particular direction. Another problem is that with low reactivity, the products do not cure quickly and cure cycles of hours are generally needed to reach >95% reaction. Generally, the low reactivity resins employed in FW processes do not achieve high glass transition temperatures (e.g. >approx. 100-110° C.) after curing.
Thus, if the automotive industry adopts FW technology, the automotive industry will need filament winding resins that provide low viscosity for easy fibre tow impregnation, a higher viscosity after winding to minimize fibre tow distortion and improve handling characteristics, demonstrate fast cure capability whilst achieving an acceptable high glass transition (Tg) temperature on final cure.